Stir in tomatoes, wine, clam juice, bay leaves and red pepper flakes to fennel mixture. Bring to a boil over medium-high heat. Cook 20 minutes or until thickened slightly and fennel is just tender, stirring occasionally.

Stir in mussels, and bring to a boil over medium-high heat. Add fish and shrimp. Return to a boil over medium-high heat; cover and cook 4 to 5 minutes or until mussels are opened and shrimp are opaque in center. Discard any unopened mussels. Remove from heat.

Gently stir in oregano and butter. Season to taste with salt and pepper, if desired. Let stand, covered, 10 minutes to develop flavors. Discard any unopened mussels. Serve in shallow bowls with crusty French bread, if desired.